Previous studies have suggested that sunlight exposure and increased vitamin D intake is associated with a reduced risk of certain cancers, particularly cancers involving the digestive system. Thirty minutes of sunlight exposure for a person with light skin can produce approximately 20,000 IU of vitamin D. Recent studies have suggested daily intake of vitamin D should be increased from 400 IU to 1000 IU.
Edward Giovannucci, M.D., Sc.D., of Harvard School of Public Health, and colleagues examined vitamin D exposure and cancer incidence for 47,800 men in the Health Professionals Follow-Up Study cohort. Between 1986 and January 31, 2000, the authors documented 4286 cases of cancer, and 2025 cancer deaths. They estimated vitamin D levels by recording each man's dietary intake and supplementation, skin pigmentation, adiposity, geographic residence, and leisure-time physical activity.
The authors observed that an increase in estimated vitamin D levels equivalent to 1500 IU of vitamin D daily, was associated with a 17% reduction in total cancer incidence, 29% reduction in total cancer mortality, and 43% and 45% reduction in incidence and mortality from digestive system cancers. Among men with the lowest vitamin D exposure, there were 758 cases of cancer diagnosed per 100,000 men and 326 cancer deaths per 100,000 annually. Among men with the highest vitamin D exposure, there were 674 cancers diagnosed per 100,000 men and 272 cancer deaths per 100,000. The authors suggest that low levels of vitamin D may be associated with increased cancer risk, and they suggest that daily supplementation with at least 1500 IU of vitamin D may be required to optimize benefits on cancer risk.
The authors write, "Confirming that vitamin D levels indeed account for the associations we observed is critical because current health recommendations typically discourage high intake of vitamin D and high levels of sun exposure, at least without use of sunscreen, which effectively blocks vitamin D production."
In an accompanying editorial, Gary G. Schwartz, Ph.D., of Wake Forest University in Winston-Salem, and William J. Blot, Ph.D., of the International Epidemiology Institute in Rockville, compliment the findings of Giovannucci and colleagues and suggest the findings support past epidemiologic observations. They write, "The promising results from both observational and laboratory studies should usher in a new era of intervention studies of vitamin D and cancer risk. Because many public health scientists are already clamoring for higher levels of vitamin D supplementation for bone and other health, randomized trials of vitamin D and cancer risk should be undertaken speedily. If the promise of vitamin D holds, a brief walk in the sun may turn out to be a step toward cancer prevention."
Article: Robin Herman, Assistant Dean of Communications, Harvard University, 617-432-4388, [email protected]
Editorial: Karen Richardson, Wake Forest University Baptist Medical Center, 313-716-4453, [email protected]